Skillful Cycling Training Induces Cortical Plasticity in the Lower Extremity Motor Cortex Area in Healthy Persons

Abstract

Cycling exercise is commonly used in rehabilitation to improve lower extremity (LE) motor function and gait performance after stroke. Motor learning is important for regaining motor skills, suggesting that training of motor skills influences cortical plasticity. However, the effects of motor skill learning in dynamic alternating movements of both legs on cortical plasticity remain unclear. Here, we examined the effects of skillful cycling training on cortical plasticity of the LE motor area in healthy adults. Eleven healthy volunteers participated in the following three sessions on different days: skillful cycling training, constant-speed cycling training, and rest condition. Skillful cycling training required the navigation of a marker up and down curves by controlling the rotation speed of the pedals. Participants were instructed to fit the marker to the target curves as accurately as possible. Amplitudes of motor evoked potentials (MEPs) and short-interval intracortical inhibition (SICI) evoked using transcranial magnetic stimulation (TMS) were assessed at baseline, after every 10 min of the task (a total of 30 min), and 30 min after the third and final trial. A decrease in tracking errors was representative of the formation of motor learning following skillful cycling training. Compared to baseline, SICI was significantly decreased after skillful cycling training in the tibialis anterior (TA) muscle. The task-induced alterations of SICI were more prominent and lasted longer with skillful cycling training than with the other conditions. The changes in SICI were negatively correlated with a change in tracking error ratio at 20 min the task. MEP amplitudes were not significantly altered with any condition. In conclusion, skillful cycling training induced long-lasting plastic changes of intracortical inhibition, which corresponded to the learning process in the LE motor cortex. These findings suggest that skillful cycling training would be an effective LE rehabilitation method after stroke.

Keywords: cortical plasticity; cycling; lower extremity; motor learning; rehabilitation; short-interval intracortical inhibition.

FIGURE 1

Experimental protocol. Eleven volunteers participated in the following three sessions on different days: (1) skillful cycling training, (2) constant-speed cycling training, and (3) rest condition. During each condition, the motor evoked potentials (MEPs) and short-interval intracortical inhibition (SICI) were measured at baseline (T0), 10 min (T10), 20 min (T20), 30 min (T30), and 60 min (T60) after the start of the experiment.

FIGURE 2

Experimental setting. A schematic diagram of the task is shown. The participants controlled the movement of a cursor on the screen by changing the pedaling speed. Pedaling movements made the cursor move upward. The participants were required to adjust the speed at which the pedals revolved to match the cursor to the target curve displayed on a screen.

FIGURE 3

Changes in motor performance. The errors in task performance during the skillful cycling session in Task 1, 2, and 3 are expressed as the area of error in arbitrary units (arb. u.). The gray lines represent individual participants. The black line and markers represent the mean data of all participants. One-factor repeated-measures ANOVA, N = 11, ^∗P < 0.05.

FIGURE 4

Changes in MEP amplitudes. Each marker represents the mean MEP amplitudes in the tibialis anterior of all participants. Error bars represent standard error.

FIGURE 5

Temporal changes in SICI between each condition. Each marker represents the mean short-interval intracortical inhibition (SICI) in the tibialis anterior. Error bars represent standard error. Two-factor repeated measures ANOVA, N = 11, ^∗P < 0.05.